Esaote O-scan eXP, User Manual

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40 / 48 Chapter 3
Quality Assurance
The image quality test, described in the chapter “System management”,
has been implemented to measure the ratio between Signal and Noise
(S/N) of a standard image, to verify the stability of system image quality.
This test is accessible to the user and should be performed after each
system start-up. It is performed periodically by Esaote technical
personnel during the maintenance procedures.
The test configuration envisages:
☛
Knee Coil 1
☛
115 mm uniform phantom. The phantom is filled with a water solution
of NiCl
2
and NaCl
☛
the sequence Test S/N - a Spin Echo sequence the parameters of which
are described in the chapter “Technical Specifications” in the manual
Image Quality and Sequences.
S/N ratio calculation: after performing the test sequence, the system
evaluates the signal as the average value of the region of interest (ROI) in
the center of the image (center of phantom) and the noise as a standard
deviation of four ROIs positioned outside the image.
The area of the signal ROI is 20x20 pixel and the area of each noise ROI is
40 x 40 pixel.
The S/N ratio is calculated as the ratio between the signal value and the
noise value defined above.
As regards the aqueous solution in the phantom, only the NiCl
2
is
potentially hazardous, but the concentration in the solution is extremely
low.
checking the of functioning the control panel every year
Maintenance Frequency